This classification means that a catastrophic failure would
likely kill someone and cause huge economic and environmental
losses. As dams continue to age, more and more dams are
considered high-hazard.

Hydropower is one of the oldest sources of renewable energy, and
most US dams were built decades ago.

Hoover Dam, perhaps the most famous, was built in 1936,
and inspired similar projects for FDR's New Deal.

Today, to repair and update just the high-hazard dams, the
Association of State Dam Safety Officials estimates it would
cost $21 billion. The association says total amount needed
to repair all dams that need updating is
$54 billion.

A
map of all the country's dams, color-coded by how hazardous they
are.FEMA

But repairing the dams can't be accomplished by a simple
government budget allotment. The government only owns 4% of the
country's dams;
69% are privately owned.

The National Dam Safety Program is tasked with overseeing dam
upgrades and distributing the money to do so. The act authorizing
program expired
in 2011, and Congress reauthorized
it in 2014. But the $9.1 million they allocated for the
program so far for fiscal year 2016 will only begin to pay for
the repairs the nation's dams need.

As John Oliver so perfectly sums up in his show on America's
failing infrastructure in March 2015: "You don't get to
cut a ribbon after routine repairs. Infrastructure is like Legos.
Building is fun; destroying is fun; but a Lego maintenance set
would be the boring f------ toy in the world."

But if we're going to keep using dams as a viable source of
renewable energy, they have to be updated.